In vascular angioplasty, a balloon catheter is threaded through a vascular lumen to the site of an occlusion. The balloon is inflated at the site to widen the lumen and then deflated and removed from the body. However, in time, the site may restenose. The restenosis may occur because the angioplasty procedure sometimes creates cracks in plaque on the vessel wall which leave jagged surfaces that can induce blood clotting at the site. Another cause of restenosis is the development of intimal proliferation. This condition is characterized by excessive cell growth that is triggered by the trauma of the angioplasty treatment.
Drugs can be administered to treat the restenosed site. One method is to administer the drug systemically, e.g., orally or intravenously. In this case, a relatively large amount of drug must be administered so that, after being diluted during transport through the body, an effective dose reaches the site. Moreover, many parts of the body which are not diseased are still exposed to the drug. Another method for administering the drug is to carry it through the body on a medical device and then release it locally at the site. In this case, the patient must suffer the discomfort and risk of a medical procedure. Moreover, the medical device must be placed in the body each time the drug is administered.